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<link rel="subsection" href="zend.filter.set.html#zend.filter.set.alnum" title="16.2.1. Alnum">
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<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="zend.filter.set"></a>16.2. Standard Filter Classes</h2></div></div></div>
<p>
        The Zend Framework comes with a standard set of filters, which are ready for you to use.
    </p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.alnum"></a>16.2.1. Alnum</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code>, removing all but alphabetic and digit characters. This filter
            includes an option to also allow white space characters.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.alpha"></a>16.2.2. Alpha</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code>, removing all but alphabetic characters. This filter includes an
            option to also allow white space characters.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.basename"></a>16.2.3. BaseName</h3></div></div></div>
<p>
            Given a string containing a path to a file, this filter will return the base
            name of the file
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.digits"></a>16.2.4. Digits</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code>, removing all but digit characters.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.dir"></a>16.2.5. Dir</h3></div></div></div>
<p>
            Returns directory name component of path.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.htmlentities"></a>16.2.6. HtmlEntities</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code>, converting characters to their corresponding
            HTML entity equivalents where they exist.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.int"></a>16.2.7. Int</h3></div></div></div>
<p>
            Returns (int) <code class="code">$value</code>
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.realpath"></a>16.2.8. RealPath</h3></div></div></div>
<p>
            Expands all symbolic links and resolves references to '/./', '/../' and extra '/'
            characters in the input path and return the canonicalized absolute pathname. The resulting
            path will have no symbolic link, '/./' or '/../' components.
        </p>
<p>
            <code class="code">Zend_Filter_RealPath</code> will return <code class="code">FALSE</code>
            on failure, e.g. if the file does not exist. On BSD systems <code class="code">Zend_Filter_RealPath</code>
            doesn't fail if only the last path component doesn't exist, while other systems will return
            <code class="code">FALSE</code>.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.stringtolower"></a>16.2.9. StringToLower</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code>, converting alphabetic characters to lowercase as necessary.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.stringtoupper"></a>16.2.10. StringToUpper</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code>, converting alphabetic characters to uppercase as necessary.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.stringtrim"></a>16.2.11. StringTrim</h3></div></div></div>
<p>
            Returns the string <code class="code">$value</code> with characters stripped from the beginning and end.
        </p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="zend.filter.set.striptags"></a>16.2.12. StripTags</h3></div></div></div>
<p>
            This filter returns the input string, with all HTML and PHP tags stripped from it, except those that have
            been explicitly allowed. In addition to the ability to specify which tags are allowed, developers can
            specify which attributes are allowed across all allowed tags and for specific tags only. Finally, this
            filter offers control over whether comments (e.g., <code class="code">&lt;!-- ... --&gt;</code>) are removed or
            allowed.
        </p>
</div>
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